This invention relates to a radiation image recording and read-out apparatus for recording a radiation image on a stimulable phosphor, exposing the stimulable phosphor to stimulating rays which cause the stimulable phosphor to emit light in proportion to the stored radiation energy, detecting the emitted light to read out the radiation image, and converting the emitted light into electric signals. This invention particularly relates to a radiation image recording and read-out apparatus wherein recording and read-out of the radiation image are carried out simultaneously. This invention also relates to a radiation image recording, read-out, and reproducing apparatus for reproducing the read-out radiation image on a recording sheet, wherein recording, read-out, and reproduction of the radiation image are carried out simultaneously.
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a recording material provided with a layer of the stimulable phosphor is exposed first to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and then is scanned two-dimensionally by stimulating rays such as a laser beam which cause the recording material to emit light in proportion to the stored radiation energy. The light emitted by the recording material upon stimulation thereof is detected photoelectrically and converted to electric image signals by a photodetector, and the radiation image of the object is reproduced as a visible image by use of the image signals on a recording medium such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
The radiation image recording and reproducing system using a recording material provided with a stimulable phosphor is advantageous over conventional radiography using a silver halide photographic material in that the image can be recorded over a very wide range (latitude) of radiation exposure. More specifically, since the amount of light emitted upon stimulation after the radiation energy is stored on the stimulable phosphor varies over a wide range in proportion to the amount of the stored energy, it is possible to obtain an image having a desirable density regardless of the amount of exposure of the recording material provided with the stimulable phosphor to the radiation, by reading out the emitted light with an appropriate read-out gain and converting it into electric signals to reproduce a visible image on a recording medium or a display device.
In the aforesaid radiation image recording and reproducing system, the recording material provided with the stimulable phosphor is used to store temporarily the radiation image in order to reproduce the final visible image therefrom on a final recording medium. For economical reasons, therefore, it is desirable that the recording material provided with the stimulable phosphor be used repeatedly.
Accordingly, the applicant proposed in, for example, Japanese Unexamined Patent Publication No. 58(1983)-200269, a radiation image recording and read-out apparatus which enables efficient circulation and reuse of the stimulable phosphor.
The proposed radiation image recording and read-out apparatus comprises, built in a single apparatus:
(a) a supporting material,
(b) at least one recording material fixed on the supporting material and comprised of a stimulable phosphor layer capable of storing a radiation image,
(c) an image recording section for exposing the recording material to a radiation passing through an object to have a radiation image of the object stored on the recording material,
(d) an image read-out section provided with a stimulating ray scanning unit for scanning the recording material carrying the radiation image stored thereon by stimulating rays, and a photoelectric read-out unit for obtaining electric image signals by reading out light emitted by the recording material scanned and stimulated with the stimulating rays,
(e) a unit for circulating the recording material on the supporting material with respect to the image read-out section for enabling reuse of the recording material by moving repeated the supporting material and the image read-out section with respect to each other, and
(f) an erasing section for eliminating the radiation energy remaining on the recording material prior to image recording on the recording material after the radiation image is read out therefrom at the image read-out section,
whereby the recording material is circulated and reused efficiently.
In the proposed radiation image recording and read-out apparatus, it is very advantageous that a material comprising an endless supporting belt and a plurality of stimulable phosphor layers overlaid on the endless supporting belt be used as the recording material. In this case, the recording material can be applied around rollers or the like and conveyed and circulated sequentially through the image recording section, the image read-out section, and the erasing section. An example of such a configuration is shown in FIG. 5.
With reference to FIG. 5, three stimulable phosphor sheets 302, 302, 302 are fixed on and endless conveyor 301. The conveyor 301 is provided around rollers 303 and 304, and moved in the direction as indicated by the arrow by rotations of the rollers 303 and 304. Around the conveyor 301, an image recording section 310, an image read-out section 320 and an erasing section 330 are disposed sequentially in the direction of conveyance by the conveyor 301.
The image recording section 310 is provided with a radiation source 311 which may be an X-ray source or the like, and stores a radiation image of an object 312 on the stimulable phosphor sheet 302 facing the radiation source 311 via the object 312. The stimulable phosphor sheet 302 carrying the radiation image thus stored thereon is sent to the image read-out section 320. The image read-out section 320 is provided with a stimulating ray source 321 for emitting stimulating rays 321A such as a laser beam, a light deflector 322 constituted by a galvanometer mirror or the like for deflecting the stimulating rays 321A emitted by the stimulating ray source 321 in the width direction of the conveyor 301, and a photodetector 323 for reading out the light 325 emitted by the stimulable phosphor sheet 302 upon stimulation thereof by the stimulating rays 321A. The photodetector 323 may be constituted by a head-on type photomultiplier, a photoelectric amplification channel plate, or the like. The photodetector 323 photoelectrically detects the light 325 emitted by the stimulable phosphor sheet 302 upon stimulation thereof and guided by a light guide member 324. When the image-recorded stimulable phosphor sheet 302 has been sent to the image read-out section 320, the stimulable phosphor sheet 302 or the scanning system for the stimulating rays 321A and the system for detecting the light 325 emitted by the stimulable phosphor sheet 302 are moved normal to the direction of scanning of the stimulating rays 321A, so that the overall surface of the stimulable phosphor sheet 302 is exposed to the stimulating rays 321A, and image read-out is carried out over the overall surface of the stimulable phosphor sheet 302. After the image read-out from the stimulable phosphor sheet 302 is finished, the stimulable phosphor sheet 302 is sent to the erasing section 330 provided with an erasing light source 331. The erasing light source 331 irradiates light having a wavelength within the stimulation wavelength range of the stimulable phosphor sheet 302 onto the stimulable phosphor sheet 302 to cause it to release the radiation energy remaining thereon. The erasing light source 331 may be constituted by, e.g., a tungsten-filament lamp, a halogen lamp, an infrared lamp, or a laser source as disclosed in U.S. Pat. No. 4,400,619. The stimulable phosphor sheet 302 erased at the erasing section 330 is sent again to the image recording section 310. In the course of movement of the stimulable phosphor sheet 302 to the erasing section 330, the stimulable phosphor sheet 302 is cleaned by a cleaning roller 305, and dust is removed from the sheet surface.
However, with the radiation image recording and read-out apparatus as shown in FIG. 5, the conveyor 301 must be stopped at the time the radiation image is to be recorded at the image recording section 310, and must be operated at the time the image read-out is to be carried out at the image read-out section 320. Therefore, it is difficult to carry out the image recording and the image read-out simultaneously. Thus the image recording cannot be carried out as long as the image read-out from a stimulable phosphor sheet is being carried out at the image read-out section 320. A comparatively long time is required for the image read-out, and therefore the image recording cannot be carried out efficiently in the case where many radiation images are to be recorded sequentially.